In the related art, there is a wireless receiver having a quadrature demodulator. A wireless receiver of one such type has a function of correcting a phase difference between an in-phase component and a quadrature component of a wireless signal (hereinafter, referred to as “IQ mismatch”), so that accuracy of received data is improved.
The IQ mismatch represents a gain error and a phase error between an I-channel signal and a Q-channel signal. This IQ mismatch is caused by inaccuracies in a 90° phase shifter in the quadrature demodulator and difference in path length between the I channel and the Q channel.
A method to correct the IQ mismatch would be to calculate a correction amount of the IQ mismatch using a phase shift circuit in a loop back circuit from the transmission side to the reception side. However, since this method requires the phase shift circuit, the total size of the wireless receiver would become larger and manufacturing cost thereof would be increased.
Another method to correct the IG mismatch would be using a thermal noise which is included in an output from a low noise amplifier. This method can improve correction accuracy of the IQ mismatch without enlarging the total size of the wireless receiver.
However, according to the method that uses thermal noise, when a disturbance wave signal such as a reception signal is generated and contained in the thermal noise, it may not be possible to detect the IQ mismatch. That is, during the reception of the disturbance wave signal, the IQ mismatch may not be correctable. For this reason, a correction parameter of the IQ mismatch has to be calculated after confirming that there is no disturbance wave signal. In other words, it is not possible to correct the IQ mismatch while the disturbance wave signal is being generated.